This invention relates to cantilever beam transducers in general and more particularly to an improved cantilever beam transducer employing an aperture on the surface and methods of fabricating such a transducer.
The prior art is replete with a number of transducer configurations which essentially are beam type transducers and as such employ an extended cantilever beam which is supported at one end and is free to deflect at the other end. The beam has deposited or otherwise secured to the surface thereof a plurality of sensors as for example piezoresistive elements. These sensors respond to a force applied to the free end of the beam to provide a resistance proportional to the applied force or pressure.
As indicated, there are many examples of such transducers which appear in the prior art. Reference is made to U.S. Pat. No. 3,654,579 issued on Apr. 4, 1972 to A.D. Kurtz et al and entitled ELECTROMECHANICAL TRANSDUCERS AND HOUSINGS. This patent is assigned to Kulite Semiconductor Products, Inc., the assignee herein. The patent shows an example of a particular type of beam transducer.
Reference is also made to U.S. Pat. No. 3,970,982 entitled BEAM-TYPE TRANSDUCERS EMPLOYING ACCURATE INTEGRAL FORCE LIMITING which issued on July 20, 1976 and is assigned to the assignee herein. In that patent there is a detailed description of the problem one experiences in controlling excessive forces applied to such beam transducers.
Reference is also made to U.S. No. 4,501,451 entitled BEAMTYPE TRANSDUCERS EMPLOYING DUAL DIRECTION FORCE LIMITING MEANS which issued on Sept. 27, 1977 to A.D. Kurtz et al and assigned to the assignee herein. This patent shows other examples of beam-type transducers which are employed in the prior art.
See also U.S. No. 3,993,150 which issued on Nov. 23, 1976 entitled ECONOMICAL WEIGHING APPARATUS EMPLOYING A CANTILEVER BEAM STRUCTURE which patent is also assigned to the assignee herein. Other patents such as U.S. No. 4,327,359 which issued on Apr. 27, 1982 and is entitled GLASS BREAKAGE DETECTORS EMPLOYING PIEZORESISTIVE DEVICES by A.D. Kurtz and assigned to the assignee herein shows particular uses for beam- or cantilever-type transducers while describing other types of such transducers.
There are also a number of cantilever devices which are fabricated from silicon wafers and have elements built in to separate the mass section from the clamping section. The hinges may constitute slots to form a silicon beam of a paddle-like configuration. Such devices have been described at conferences by the University of Stanford, Calif.
As one can ascertain, cantilever- or beam-type transducers are widely employed and used for many different purposes as for measuring force or pressure applied to a beam or other device and have been widely utilized in the prior art. Suffice it to say that it would be extremely desirable to produce a cantilever beam transducer which operates in an efficient manner to detect relatively small forces applied thereto and which transducer exhibits many desirable features such as force limiting in dual directions.
It is a further object to provide a method for fabricating cantilever transducers in large quantities. The method to be described lends itself to the production of accurate and efficient transducers employing cantilever structures which can be batched or mass produced according to the techniques to be described.